I have three tubs going outside right now two are in the shade and one is in full sun. Yesterday when I went to check on them, the one that's in full sun was quite warm. It has a lotus and a couple of small water lettuce. Right now the Lotus only has 4 floating leaves, and the water lettuce are quite small - so the plant material is not yet shading the water. The guppies weren't showing any signs of distress yet, but the weather is going to get a lot warmer before the lotus sends up enough large leaves to shade the water sufficiently.

What is the highest temperature you think guppies could take comfortably?_________________Maura
"You did then what you knew how to do and when you knew better... you did better!" -Maya Angelou